1. Technical Field of Invention
The present invention generally relates to a solid end mill and more particularly, to a solid end mill having a tool main body with cutting edges at ridge portions formed on an outer periphery of the tool main body, wherein a chip discharge flute is formed between adjacent cutting edges so that the solid end mill may be used in slot or shoulder milling of work materials.
2. Discussion of Background
A tool main body 1 of a conventional solid end mill is shown in cross-section in FIG. 11 and the tool main body 1 is nearly cylindrical. The cross-section is taken at some point along the length of the end mill so as to be perpendicular to the central longitudinal axis O of the tool main body 1. The solid end mill has four teeth (i.e., the ridge portions with cutting edges) alternating with four chip discharge flutes 2. The four teeth are each formed at equally spaced intervals with respect to each other so as to protrude from the outer periphery of the tool main body 1. The four chip discharge flutes 2 are also each formed at equally spaced intervals with respect to each other around the outer periphery of the tool main body 1. Each chip discharge flute 2 of the tool main body 1 has a wall surface facing a tool rotational direction T. The wall surface facing the tool rotational direction T forms a rake face 3. The cutting edges 5 are formed along the tip of the ridge portions where the rake face 3 intersects the flank face 4. Each of the ridge portions extends radially outwardly from a core thickness circle R (i.e., the outer cylindrical outline) of the tool main body 1.
The rake face 3 forms a concavely curved surface adjacent to the flute bottom 6, as is shown in FIG. 11. The rake face 3 meets the flute bottom 6 of the chip discharge flute 2 at a location where the chip discharge flute 2 is depressed so that the flute bottom 6 of the chip discharge flute 2 is tangent to the core thickness circle R of the tool main body 1. Thus, the portion of the chip discharge flute 2 from the flute bottom 6 to the cutting edge 5 engages the outer surface of the chip C so that the flank face 4 of the next cutting edge 5 is stretched in the tool rotational direction T when the rake face 3 is stretched. In addition, the chip discharge flute 2 is generally formed so as to curve towards the opposite direction of the tool rotational direction T of the tool main body 1. In other words, the chip discharge flute 2 extends towards the back end of the tool main body 1. Consequently, a cutting edge 5 is formed spirally around the central longitudinal axis O of the tool main body 1.
In the conventional solid end mill of the structure as discussed above and as shown in FIG. 11, the chip C, which is generated by the cutting edge 5 at the time of cutting, reaches the flute bottom 6 by sliding or rubbing on all of the surfaces of the rake face 3, including along the concavely curved portion of the rake face 3. The flute bottom 6 is curled during the sliding or rubbing of the surfaces of the rake face 3 so that a chip C is discharged from the chip discharge flute 2, as shown in FIG. 11. However, the type of material that the end mill is used to cut or drill through influences the results of the cutting or drilling. For example, when the work material to be cut or drilled through is aluminum, it is highly likely that adhesion of aluminum will occur on the rake face due to the heat of friction generated during the sliding or rubbing of the chip C on all of the surfaces of the rake face 3. Consequently, the useful life of the tool may often be unnecessarily shortened.
The present invention has been made with the above-described problems of the prior art in mind, and aims to provide a solid end mill for prolonging the useful life of the tool main body, by preventing adhesion, even if the work material being cut or drilled through is aluminum.
In order to solve the above-described problems of the prior art, the present invention provides a solid end mill, which includes: a tool main body having a central longitudinal axis, wherein the tool main body is nearly cylindrical and the tool main body rotates around the central longitudinal axis thereof; a chip discharge flute formed at an outer periphery of the tool main body; a cutting edge formed at a ridge portion on the outer periphery of the tool main body, wherein a wall surface adjacent to the cutting edge is a rake face of the chip discharge flute and the wall surface faces the tool rotational direction. In a first embodiment of the present invention, a convex portion is formed on the rake face so as to extend radially outwardly from an adjacent concavely curved portion, wherein the rake face stretches from the cutting edge to the flute bottom of the chip discharge flute. The convex portion may be any one of many different shapes, such as rounded, triangular, trapezoidal, etc. In a second embodiment of the present invention, a concave portion is formed adjacent to the concavely curved portion of the rake face, wherein the rake face stretches from the cutting edge to the flute bottom of the chip discharge flute.
In operation of the first embodiment of the present invention, a chip contacts the convex portion of the rake face of the solid end mill, and then passes over the concavely curved portion of the rake face in the solid end mill, so that a clearance is generated between the chip and the rake face. Thus, the heat of friction, caused by sliding or rubbing of the chip, is inhibited and adhesion is prevented. In addition, since the convex portion is formed at the bottom of the chip discharge flute (i.e., the location stretching from the flute bottom of the rake face to the concavely curved portion of the rake face, the concavely curved portion being adjacent the cutting edge), a clearance is created at a location between the convex portion and flute bottom in order for the heat of friction due to sliding or rubbing of the chip to be controlled much more certainly.